Dear all,

during the admittance measurement on a p-type component GaxIn1-xAs solar cells irradiated with different particles of different energies and at various fluences, I got a Cf curve as shown on the graph below.

Component cells are referred to as iso-type cells and they represent individual sub-cells of multi-junction solar, but the p-n junction is only formed at the sub-cell of interest (in this case GaxIn1-xAs), whereas the remaining subcells are present but they do not have a formed p-n junction.

At high temperatures, during admittance measurement, a peculiar behaviour is evident in the low-frequency region of the Cf graph. Normally, the capacitance gradually decreases as the frequency increases, eventually, the defect states not being able to follow the modulation of free carriers at higher frequencies. Here, a capacitance step will appear as the frequency moves from low to high.

However, in the graphs, the capacitance first increases, and it is followed by a gradual decrease, resulting in a distinctive "hump" shape.

This behaviour can be partially "flattened" in the low-frequency region by annealing.

I was wondering if anyone has come across such curves during their research and what could be the possible reasons for such a defect behaviour.

Thank you,

Denisa